In the printing press field, particularly in rotary web-fed presses, a web is fed from a continuous roll of paper into the printing press. The web passes through various processing units, such as the infeed, print units, dryer, chill unit, folders, slitter, cutter, stacker, and other processing units as it is formed into signatures and then into the final printed product. Typically, the web is cut and folded during the processing of the product. After the web has been cut, the individual products are referred to as signatures. Signatures may be processed further by additional cutting and folding units. One particular process area, for example, is the collect cylinder and jaw cylinder nip.
Signatures may be fed into the collect cylinder (also referred to as a gripper and tucking blade cylinder or a transfer cylinder) and jaw cylinder nip by a tape drive system, as is known in the art, and described, for example, in co-pending application Ser. No. 08/645,855, which is incorporated in its entirety herein by reference. Tape drive systems typically include a number of tapes on each side of the product (e.g., signature) that are spaced longitudinally across driven rollers and that form a loop around the driven rollers, the rollers being driven by the collect cylinder circumference. The tapes contact a signature and provide a motive force to the signature on both sides by surface friction between the tape and the signature.
U.S. Pat. No. 4,521,007 describes a braking brush used in a folding apparatus of a rotary printing press that includes a puncturing or first product guiding cylinder which grips individual signatures and guides the signatures to a folding or second product guiding cylinder. The braking brush assembly of that patent uses braking brushes for stretching signatures which are conveyed in a given direction on the folding cylinder. The braking brushes are disposed individually at each folding cylinder, are curved to match the curvature of the folding cylinder, and are distributed over the length of the folding cylinder. The apparatus also includes a spindle and a cross bar extending transversely to the direction in which the signatures are conveyed. The braking brushes are movably fastened at a lower end to the spindle and at upper ends to the cross bar. Levers press the braking brushes to a greater or lesser extent selectively against the signatures conveyed on the cylinder.
During normal operation of a printing press, signatures may be fed through a tape drive mechanism and into a further processing nip such as a collect cylinder to jaw cylinder nip. However, at start-up, before the press is running at normal operating speeds (e.g., steady state), signatures in the tape drive mechanism do not travel in the same manner as when they travel at normal operating speed. Namely, a signature starting from rest or traveling at low speeds through the tape drive mechanism may not properly enter the further processing nip as the signature exits the tape drive mechanism. Improper travel of the signature (e.g., the lead edge is not under a gripper and thus is not guided to the next processing area) often results in paper jams which necessitate undesirable shutdown of the printing press. In addition, there is a certain amount of time (e.g., up to 30 seconds) required when the folder is seeking phase with respect to the printing unit. Each print unit has its own drive motor and the timing is established electronically. Any timing or phasing changes must be made gently so as not to break the web or ribbons.
An object of the present invention is to provide an apparatus that prevents jams in the folder apparatus during start-up or deceleration periods of press operation.